Silicon carbide has attracted many researchers' interest around the world due to its remarkable chemical, mechanical and field emission properties. For example, silicon carbide is currently used as a base material for diesel engine exhaust filters and is a representative material for high-strength, high-toughness structures. Under such circumstances, the amount of money being spent to manufacture silicon carbide-related products is steadily increasing year after year, suggesting that silicon carbide is considered to be worthy of research and to be of commercial value.
Silicon carbide has been produced and used in a bulk or thin film form.
Silicon carbide on a nanometer scale has high specific surface area and high strength per unit area unachievable by bulk silicon carbide. When nanometer-sized silicon carbide is applied to electronic devices, they can show excellent characteristics, such as field emission effects and quantum confinement effects, which are those inherent to nanowires.
Since a Japanese research group led by S. Iijima has first reported on carbon nanotubes in 1991 (S. Iijima, Nature, 1991), numerous studies have been conducted on one-dimensional nanostructures (e.g., nanowires) throughout the world.
C. M. Lieber research group, Harvard University, presented the first report on silicon carbide nanostructures in 1995 (C. M. Lieber, Nature, 1995). Specifically, the research group reported methods for the synthesis of silicon carbide nanowires using carbon nanotubes. Since then, a great deal of research and development aimed at the synthesis of silicon carbide nanowires has been conducted to date.
Korean Patent Application No. 2004-70373 suggests a method for the production of silicon carbide nanowires coated with high-purity, high-density carbon by dissolving nickel nitrite hexahydrate as a catalyst in an alcohol, applying the catalyst solution to a silicon substrate, putting the catalyst-coated silicon substrate and a mixture of a tungsten oxide powder and a carbon powder in a sapphire boat, heating the sapphire boat while feeding an inert gas into the sapphire boat, and cooling the heated sapphire boat to room temperature.
According to the method, however, amorphous films, oxide films or particles remain adsorbed on the surfaces of silicon carbide nanowires and the metal used as catalyst is left behind, resulting in a deterioration in the physical properties of the silicon carbide nanowires.
Only a few of the reported technologies associated with the synthesis of silicon carbide nanowires have been successful in the fabrication of devices using silicon carbide nanowires. Current research is applied at the laboratory level and more research is still needed.
Further, since most of the technologies are associated with the fabrication of semiconductor devices, actual difficulties exist in the application to a series of semiconductor manufacturing processes due to high growth temperatures of silicon carbide. Moreover, the use of highly priced apparatuses for the growth of silicon carbide makes a commercial approach to the fabrication of semiconductor devices difficult.
Furthermore, the use of expensive silica with a purity as high as 99.9% as a raw material for silicon carbide and an additional crystallization catalyst renders the production procedure complex and causes a marked increase in production cost.
In conclusion, silicon carbide nanowires have not yet been put to practical use in many applications despite their excellent physical properties.